Without a doubt the most debated and highly contested Quality Level of all is QL-C……at least it was with the original 38-02, but hopefully that will all change with the new 38-21!
Quality Level ‘C’ (QLC) is commonly defined as surveying visible above ground utility facilities (e.g., manholes, valve boxes, etc.) and correlating this information with existing utility records (QL-D information).
Seems simple but it is amazing how confusing it can get. The soon to be published 38-21 version does a good job at clarifying QLC and providing commentary to help users further understand it and how to apply it to drawings.
Here is a basic guide to understanding it. QLC is most typically used on sewer networks. We can survey the MH lid, we can open the lid to confirm the location of the pipes coming in and out of the chamber, and we can use records to “connect the dots” between two MH’s. That line that connects the dots can then be labelled QLC if the engineer deems that all necessary criteria are met (pipe sizes, materials are consistent with records, etc.). There are other utilities where QL-C is used, like large diameter watermains or gas mains where you can survey inline valves to determine the location. Things like telecom, and electrical are rarely if ever shown at QLC for the simple reason that the surface features associated with them like pedestals and MH lids do not necessarily help to confirm the underground alignment and therefore work is usually done to try to depict them at QLB and if that is not possible they are shown at QLD.
I hope that provides some clarifications. Next up will be QLB, the workhorse so to speak of the ASCE 38 standard!